A common type of irrigation sprinkler, referred to as a rotor-type sprinkler, has an outer cylindrical casing that is buried in the ground and a central telescoping riser that pop ups to irrigate the adjacent turf or landscaping. The riser typically encloses a turbine, reduction gear train and reversing mechanism which oscillate a cylindrical turret or head that is rotatably mounted at the upper end of the riser and contains a nozzle. The upper circular surface of the turret often has an elastomeric disk attached to the upper surface thereof which provides some degree of cushioning if a person should fall onto the sprinkler, particularly when the sprinkler is located in a playing field. The elastomeric disk usually has one or more cross-hair slits that allow a tool, such as the HUNTER® tool, to be inserted for adjusting the arc of coverage of the sprinkler and for lifting the riser when the water is OFF. This arrangement provides a degree of contamination protection because when the tool is withdrawn from the cross-hair slits they return to their planar condition and restrict soil, insects and other debris from entering into the passage leading to the arc adjustment mechanism. In addition to an elastomeric cover, some commercial rotor-type sprinklers have included an elastomeric cylindrical sleeve that covers a reduced diameter upper portion of the body cap that screws over the outer cylindrical case and holds the riser within the outer case. This elastomeric sleeve is held in place by a hard plastic retainer ring which is typically fixed in position by sonic welding.
Pop-up rotor-type sprinklers are typically installed in the ground so that the top surface of the sprinkler is close to the top surface of the ground. This ensures that they will not be clipped by mower blades and also reduces the likelihood that people will trip over the sprinklers. It is frequently necessary to service a conventional rotor-type sprinkler by unscrewing the body cap so that the riser and other components can be removed, repaired and replaced. The ribs on the body cap are typically below the top surface of the ground and are covered with wet soil. However, the hard plastic retainer ring significantly impedes the ability to grip the body cap and unscrew the same. Since the ribs are typically uncovered hard plastic, they are slick and difficult to grip.